The present disclosure relates to a direct current/direct current (DC/DC) converter.
In electronic apparatus such as a personal computer and a game dedicated machine, a DC/DC converter (switching regulator) that steps down a DC voltage supplied from a battery or an inverter to the optimum voltage level for a load is utilized.
FIG. 1 is a circuit diagram showing a configuration example of a buck DC/DC converter on which the present inventors have made studies. A DC/DC converter 2r of FIG. 1 is a multiphase DC/DC converter and includes an input line 4, an output line 6, N switching circuits SW1 to SWN, N inductors L1_1 to L1_N, output capacitors Co, a phase controller 16, an oscillator 18, a pulse modulator 20, and a distributor 22.
The DC/DC converter 2r steps down an input voltage VIN of the input line 4 to a predetermined level and supplies an output voltage VOUT to a load (not shown) connected to the output line 6. To the input line 4, an input capacitor Ci for stabilizing the input voltage VIN is connected. To the output line 6, the output capacitors Co for smoothing the output voltage VOUT are connected.
The plural switching circuits SW1 to SWN each include a switching transistor M1, a synchronous rectifier transistor M2, and a driver DRV. The i-th switching circuit SWi performs switching of the two transistors M1 and M2 in a complementary manner to generate a switching voltage VSWi at the connecting node of the two transistors (switching node).
The inductors L1_1 to L1_N are each provided for a respective one of the switching circuits SW1 to SWN. The i-th inductor L1—i is provided between the switching node of the corresponding switching circuit SWi and the output line 6.
The oscillator 18 generates a periodic signal SOSC having a predetermined frequency. The pulse modulator 20 is e.g. a pulse width modulator and generates a pulse signal SPWM in synchronization with the periodic signal SOSC based on a feedback voltage VFB depending on the output voltage VOUT. For example the feedback voltage VFB is a voltage obtained by dividing the output voltage VOUT by resistors R1 and R2. The pulse modulator 20 adjusts the duty ratio of the pulse signal SPWM so that the feedback voltage VFB may correspond with a predetermined reference voltage VREF. By this feedback control, the output voltage VOUT is stabilized to a target level VREF×(R1+R2)/R2.
The phase controller 16 sets the number K of drive phases. For example in the case of N=4, K can be selected from four values of 1, 2, 3, and 4.
The distributor 22 selects K switching circuits among the N switching circuits SW1 to SWN and distributes pulse signals SPWM1 to SPWMK to each of the selected K switching circuits with a phase difference of (360/K) degrees.
The configuration of the DC/DC converter 2r is as described above. Next, the operation thereof will be described. Here, a case in which N=4 and the number K of drive phases can take 2, 3, and 4 will be described. FIGS. 2A to 2C are waveform diagrams showing switching voltages VSW1 to VSW4 when K=2, 3, and 4, respectively.